Toxicity Interaction Mechanism Of Microplastics And Pharmaceutical Active Compounds On Tilapia

Microplastics(MPs)exist stably in the environment for a long time,causing varying degrees of toxic effects on organisms.However,information about the biological effects of MPs on freshwater organisms remains limited.Pharmaceutical active compounds(Ph ACs)is a kind of new pollutants widely existing in various environmental media.Although environmentally relevant concentrations of them in aquatic environment were low,long-term exposure to antibiotics may produce bioaccumulation effects in non-target aquatic organisms,thus affecting physiological processes in organisms at the genetic and molecular levels because of their special pharmacological and physiological functions.In addition,MPs in the environment will experience the aging process of light,wind and wave impact,which will cause irreversible physical and chemical properties changes on the surface of MPs,and then affect the compound pollution behavior of MPs and Ph ACs.So the ecological risk caused by them could not be ignored.In this study,three kinds of PS-MPs with different particle sizes(0.3,5,70–90 ?m)were selected as the stress factors,and tilapia were used as the model organism to investigate the size effect toxicity of MPs on tilapia;Based on the above,the UV irradiation aging of 5 ?m PS-MPS was carried out.The adsorption behaviors of two typical Ph ACs propranolol(PRP)and sulfonmethoxazole(SMX)were studied;Finally,the toxic effects of PS-MPs and Ph ACs on tilapia were studied.The contents and main conclusions of the study are summarized as follows:1.Toxicological effects of PS-MPs with different particle sizes on tilapiaIn this chapter,fish were exposed to clean water and PS-MP treatments with concentration of 100 ?g/L and particle size of 0.3,5 and 70–90 ?m,respectively.The accumulation of PS-MPs in different tissues of tilapia and its biochemical effects on tilapia were studied.The following results were obtained:(1)Three different sizes of MPs accumulated in the tissues of tilapia(liver,gut,brain and gills)in different degrees,suggesting that MPs can pass through the intestinal barrier and blood-brain barrier in some way.And eventually accumulated in the liver and brain of tilapia;(2)In the treatments of 5 and 70–90 ?m PS-MPs,more SOD was induced and the overproduction of MDA was found.This result indicates that larger size PS-MPs can induce more severe oxidative stress than PS-MPs with smaller size;(3)During the entire exposure period,the treatment of 0.3 ?m MPs could always inhibit the BFCOD activity,and the inhibition rate reached 18.1% on 14 d.For the 5 and70–90 ?m MP treatments,the BFCOD activity first increased and then decreased with time,suggesting that smaller PS-MPs can significantly inhibit the activity of CYP3 A related enzymes,the CYP3 A enzyme in the liver may not be sensitive to larger MPs;(4)After the exposure,there was no significant difference in ACh E activity between the treatments of 0.3,5,and 70–90 ?m PS-MPs,the inhibition rates were 14.5%,21.0%,and 9.1%,respectively.This result suggested that MPs had an effect on ACh E activity and the size-dependent effect of suppression is not obvious;(5)After 14 days of exposure,31,40,and 23 metabolites with significant differential expression were produced in the 0.3,5,and 70–90 ?m MPs exposure groups,respectively.The metabolic pathway of tyrosine was effected by these three PS-MPs treatments.2.Study on the interaction between aged MPs and selected Ph ACsIn this chapter,5 ?m PS-MPs were irradiated by UV light,and the changes on the surface and microstructure of MPs before and after aging were analyzed.Then,the adsorption behavior of MPs(virgin and aged)for PRP and SMX were investigated.(1)After the virgin PS-MPs were irradiated with UV light for 240 h,the specific surface area and pore volume increased by 0.27 and 0.16 times,respectively,and obvious peaks appeared in the band corresponding to the characteristic carbonyl group.These results indicated that the UV aging process increases the pore structure,pore volume and oxygen-containing functional group of MPs;(2)The adsorption of PRP and SMX by both virgin and aged MPs underwent three stages:(1)In the first 0.5 h of the adsorption process,the adsorption rates for PRP and SMX by MPS(virgin and aged)were faster;(2)In the 0.5-4 h of the adsorption process,the adsorption rates of MPs decreased gradually;(3)After 4 h of the adsorption process,the MPs adsorption of pharmaceutical reached equilibrium.(3)The adsorption kinetics of virgin and aged MPs for PRP and SMX both conform to the pseudo-second-order kinetics model,which indicates that there is chemical adsorption in the adsorption process;(4)The equilibrium adsorption concentration of virgin and aged MPs on PRP are1884.93 and 1927.77 ?g/g,respectively,and the equilibrium adsorption concentration of virgin and aged MPs on SMX is 1882.09 and 2024.18 ?g/g,which shows that compared with virgin MPs,the aging process can be improved the adsorption performance of MPs on PRP and SMX.3.Study on the biological effects of aged MPs and selected Ph ACs on tilapiaFish were exposed to clean water,PRP alone,SMX alone,MP(virgin and aged)alone and four co-exposure treatements respectively.The joint toxicological effects of MPs(virgin and aged)and pharmaceutical on tilapia were compared.The following results were obtained:(1)After the exposure,the accumulation of MPs in all treatments followed the order of liver>brain>gills>gut,which indicates that the accumulation mode of MPs in tilapia would not change due to the aging of MPs and the presence of pharmaceutical;(2)Compared with the co-exposure of virgin MPs for 14 days,aged MPs increased the accumulation of PRP in the tilapia brain by 82.3%,and decreased the accumulation of SMX in the gills by 46.1%,indicating that aging will the effect MPs on the accumulation of pharmaceutical in tilapia;(3)The IBR values of VM-PRP and AM-PRP in the treatments were 8.39 and 6.81,respectively,which indicated that the stress of MPs and PRP on tilapia could be alleviated by the aging of MPs,and was mainly related to the production of relatively low neurotoxicity and lipids.The IBR values of VM-SMX and AM-SMX in the treatment group are 4.33 and 7.41,respectively,which indicates that aging will increase the stress of MPs and SMX to tilapia,and it is mainly related to the higher inhibition of cytochrome P450 enzyme activity caused by co-exposure of aged MPs and SMX.(4)MPs aging mainly influenced the expression of genes related to the metabolic process,immune system process,and the genetic information process under the co-exposure to MPs and pharmaceuticals.